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# Objective - Fixes #7680 - This is an updated for https://github.com/bevyengine/bevy/pull/8899 which had the same objective but fell a long way behind the latest changes ## Solution The traits `WorldQueryData : WorldQuery` and `WorldQueryFilter : WorldQuery` have been added and some of the types and functions from `WorldQuery` has been moved into them. `ReadOnlyWorldQuery` has been replaced with `ReadOnlyWorldQueryData`. `WorldQueryFilter` is safe (as long as `WorldQuery` is implemented safely). `WorldQueryData` is unsafe - safely implementing it requires that `Self::ReadOnly` is a readonly version of `Self` (this used to be a safety requirement of `WorldQuery`) The type parameters `Q` and `F` of `Query` must now implement `WorldQueryData` and `WorldQueryFilter` respectively. This makes it impossible to accidentally use a filter in the data position or vice versa which was something that could lead to bugs. ~~Compile failure tests have been added to check this.~~ It was previously sometimes useful to use `Option<With<T>>` in the data position. Use `Has<T>` instead in these cases. The `WorldQuery` derive macro has been split into separate derive macros for `WorldQueryData` and `WorldQueryFilter`. Previously it was possible to derive both `WorldQuery` for a struct that had a mixture of data and filter items. This would not work correctly in some cases but could be a useful pattern in others. *This is no longer possible.* --- ## Notes - The changes outside of `bevy_ecs` are all changing type parameters to the new types, updating the macro use, or replacing `Option<With<T>>` with `Has<T>`. - All `WorldQueryData` types always returned `true` for `IS_ARCHETYPAL` so I moved it to `WorldQueryFilter` and replaced all calls to it with `true`. That should be the only logic change outside of the macro generation code. - `Changed<T>` and `Added<T>` were being generated by a macro that I have expanded. Happy to revert that if desired. - The two derive macros share some functions for implementing `WorldQuery` but the tidiest way I could find to implement them was to give them a ton of arguments and ask clippy to ignore that. ## Changelog ### Changed - Split `WorldQuery` into `WorldQueryData` and `WorldQueryFilter` which now have separate derive macros. It is not possible to derive both for the same type. - `Query` now requires that the first type argument implements `WorldQueryData` and the second implements `WorldQueryFilter` ## Migration Guide - Update derives ```rust // old #[derive(WorldQuery)] #[world_query(mutable, derive(Debug))] struct CustomQuery { entity: Entity, a: &'static mut ComponentA } #[derive(WorldQuery)] struct QueryFilter { _c: With<ComponentC> } // new #[derive(WorldQueryData)] #[world_query_data(mutable, derive(Debug))] struct CustomQuery { entity: Entity, a: &'static mut ComponentA, } #[derive(WorldQueryFilter)] struct QueryFilter { _c: With<ComponentC> } ``` - Replace `Option<With<T>>` with `Has<T>` ```rust /// old fn my_system(query: Query<(Entity, Option<With<ComponentA>>)>) { for (entity, has_a_option) in query.iter(){ let has_a:bool = has_a_option.is_some(); //todo!() } } /// new fn my_system(query: Query<(Entity, Has<ComponentA>)>) { for (entity, has_a) in query.iter(){ //todo!() } } ``` - Fix queries which had filters in the data position or vice versa. ```rust // old fn my_system(query: Query<(Entity, With<ComponentA>)>) { for (entity, _) in query.iter(){ //todo!() } } // new fn my_system(query: Query<Entity, With<ComponentA>>) { for entity in query.iter(){ //todo!() } } // old fn my_system(query: Query<AnyOf<(&ComponentA, With<ComponentB>)>>) { for (entity, _) in query.iter(){ //todo!() } } // new fn my_system(query: Query<Option<&ComponentA>, Or<(With<ComponentA>, With<ComponentB>)>>) { for entity in query.iter(){ //todo!() } } ``` --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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